1. Field of the Invention
The present invention relates to microparticulate hydrocolloids, having particular utility as fat replacement components in comestibles.
2. Statement of Related Art
The literature and patent records are replete with discoveries in the field of hydrocolloids, including microparticulate forms thereof.
Many techniques have been used to prepare hydrocolloid microparticles, such as spray processes and emulsion processes. See, e.g. PCT WO 91/19424; EP-A 0437360 A1; U.S. Pat. Nos. 5,082,684; 4,956,128; J. C. Ogbanna et al., "Production of Micro-Gel Beads by a Rotating Disk Atomizer", J Ferment Bioeng. 68(1), 40-48, 1989; R. M. Buitelaar, A. C. Hulst, and J. Tramper, "Immobilization of biocatalysts in thermogels using the resonance nozzle for rapid drop formation and an organic solvent for gelling", Biotechnology Techniques 2(2), 109-114, 1988; H. Su, R. Bajpai, and G. W. Preckshot, "Characterization of Alginate Beads Formed by a Two Fluid Annular Atomizer", Applied Biochemistry and Biotechnology, 20/21, 561-569, 1989; P. Audet and C. Lacroix, "Two-phase Dispersion Process for the Production of BioPolymer Gel Beads: Effect of Various Parameters on Bead Size and Their Distribution", Process Biochemistry, December 1989, 217-226; M. R. Chaudhari et al., "Preparation of Crosslinked Starch Beads as a Medium for Gel Filtration", Starch/Starke, 41(11) 415-416, 1989; S. Hjerten, "The preparation of agarose spheres for chromatography of molecules and particles", Biochem. Biophys. Acta., 79, 393-398, 1964; Y. Motozato, "Beads of cross-linked glucomannan and production thereof", U.S. Pat. No. 4,882,426 (Nov. 21, 1989); and British Patent No. 1,577,955 to Takeda Chemical Industries.
In addition, the following references describe methods for encapsulating other materials within the microparticles:
U.S. Pat. No. 4,956,128 ti Hommel et al.; U.S. Pat. No. 4,143,201, U.S. Pat. No. 3,936,573 to Brocket; I. Chibata, J. Kato, and M. Wada, "Method for Producing Ethanol with Immobilized Microorganism", U.S. Pat. No. 4,350,765 (Sep. 21, 1982); M. Wada, J. Kato and I. Chibata, "A New Immobilization of Microbial Cells", Eur J. Appl. Microbiol Biotechnolog, 8, 241-247 (1979); A. R. Navarro, M. C. Rubio, and D. A. S. Callieri, "Production of Ethanol by Yeasts Immobilized in Pectin", Eur J. Appl. Microbiol Biotechnology, 17, 148-151 (1983); K. Nilsson et al., "Entrapment of animal cells for production of monoclonal antibodies and other biomolecules", Nature 302, 629-30, 1983; and K. Mosbach, and K. Nilsson, "A method of encapsulating bio material in bead polymers", PCT Application WO 83/03102 (Sep. 15, 1983). Tiemstra U.S. Pat. No. 3,573,058 discloses a codried mixture of microcrystalline cellulose and small quantities of a hydrocolloid. U.S. Pat. No. 4,192,900 discloses starch particles comprising starch mixed with a gelling hydrocolloid.
The following references relate to specialized techniques for drying hydrocolloid microparticulates in order to try to prevent agglomeration of the microparticulates which will otherwise occur:
British patent No. 887,901 to F. Hoffman-La Roche & Co. (CA 56, 9179 i(1961)) discloses emulsions of a gelling colloid, including pectin and algin, which are dried into particles by spraying or atomizing into a gas at least 10.degree. below the t.sub.m of the resultant gel, and the particles are kept separate in free fall for at least 15 seconds for gelling to begin. Nelson U.S. Pat. No. 2,438,450 discloses a drying technique for microparticulates comprising mixing with the hydrated microparticulates a quantity of previously dried microparticulates to prevent agglomeration of the hydrated microparticles. V. Ghetie and H. D. Schell, "Drying of Agarose Gel Beads", Experientia 27(12), 1384-5, 1971 discloses agarose microparticles which are acetone washed, then air dried at room temperature.
In addition to the above specialized drying techniques for minimizing agglomeration problems, other techniques have been used to try to prevent agglomeration of hydrocolloid microparticles. For example, Singer et al. U.S. Pat. No. 5,153,020, discloses water-dispersible spheroidal macrocolloid microparticles as a fat substitute with which "aggregate blocking agents" such as lecithin, pectin, xanthan gum, and carboxymethylcellulose, are added to the macrocolloid particles to stabilize the particles in the hydrated form in which the particles are manufactured and employed as fat substitutes.
U.S. Pat. No. 4,911,946 discloses the use of aggregate blocking agents such as lecithin and xanthan gum in hydrated spheroidal carbohydrate microparticles to produce the mouth feel of fat/cream.
The following references disclose microparticles containing an inner core which can be a hydrocolloid, and an outer hydrophobic coating of a digestible fat: U.S. Pat. No. 4,305,964; EP-A 0 011 345; and EP-A0 380 225.
U.S. Pat. No. 3,527,712 discloses a process of preparing chromatography-size agarose beads by including within an agarose gel a macromolecular hydrocolloid such as sodium alginate, potassium lambda carrageenan, carrageenan, hydroxymethylcellulose, sodium carboxymethylcellulose, and the like. Upon drying the agarose beads the macromolecular hydrocolloid becomes coagulated within the pore of the agarose. Upon rehydration, the macromolecular hydrocolloid dissolves, leaving the porosity of the gel substantially intact for its intended use in chromatography.
Renn et al U.S. 4,952,686, discloses an alloy gum of cassia gum and a gelling and thickening agent such as carrageenan, agar, agarose, hydroxyethylcellulose, carboxymethylcellulose, dextran, and the like. This alloy gum when dried and ground into a powder can be readily dissolved in water to form a clear, stable colloidal solution.
Japanese patent publication 04/08,257 (92/08,257) (CA 116: 172746C) discloses the manufacture of dry konjac, which can be soaked in water to restore its original state and organoleptic properties, by mixing konjac with mono- and/or oligosaccharides such as glucose, sucrose, maltose, lactose and fructose, and then drying the mixture.
WO 91/19424 (PCT published application) discloses hydrated microparticulate beads as a fat substitute composed of a hydrous hydrocolloid gel, a metal capable of causing gellation, and an ionic polysaccharide such as alginate, pectate, and sodium carboxymethylcellulose.
Despite the extensive art as exemplified above relating to hydrocolloids and microparticulate forms thereof, no universally applicable techniques for drying and rehydrating such microparticulates without resulting in agglomeration of the microparticles and failure to disperse in water have been disclosed in the art. This is perhaps not surprising since gel-forming hydrocolloid microparticles exhibit very strong propensities to aggregate when wet or even in the presence of limited moisture such as when the dry microparticles are stored in contact with air. In fact, microparticulates made from gel-forming hydrocolloids alone cannot be dried and then rehydrated without specialized drying techniques to prevent agglomeration, since the dried agglomerates will not disperse or will disperse very poorly in the presence of water upon attempted rehydration. Agglomerated microparticulates cannot be used as a fat substitute since they do not possess the required organoleptic properties. It is therefore essential that dried microparticulates be capable of rehydration to their original size and shape in order to closely mimic the organoleptic properties of fat, especially in oil-in-water emulsions. This problem of agglomeration when rehydrated is not shared, or is shared to only a limited extent, with larger size hydrocolloid particles such as those disclosed in U.S. Pat. Nos. 3,527,712 and 4,952,686.